Porosity Gradient Preform for Uniform Composite Densification
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Solution Overview
Problem
Existing high temperature composite manufacturing methods face challenges in achieving uniform densification due to limited pathways for gas infiltration, leading to components with greater than 10% porosity.
Innovation Solution
A porosity gradient fibrous preform is created by arranging multiple fabric-resin layers with varying resin compositions and char yields, resulting in a sequentially increasing porosity from the center to the outer surface, which facilitates uniform gas infiltration during densification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dry fabric preform is used with uniform structure, then manufacturing is simple, but gas infiltration pathways are limited leading to non-uniform densification and high porosity (>10%)
Solution Approach 1:
The preform incorporates fabric layers with different resin compositions and char yields at different locations (inner vs outer layers), creating a spatially varying porosity gradient that facilitates uniform gas infiltration throughout the preform thickness, directly resolving the densification uniformity issue
Solution Approach 2:
The preform is divided into multiple fabric-resin layers with distinct resin formulations (e.g., phenolic, epoxy, polyimide) and different char yields (5-15%, 15-25%, 25-35%), creating segmented regions with controlled porosity differences that guide gas flow pathways for uniform densification
2Manufacturing precision
If multiple fabric-resin layers with different resins are used to create porosity gradient, then gas infiltration pathways are improved for uniform densification, but manufacturing complexity increases
Solution Approach 1:
The resin selection and layer arrangement are predetermined in the preform design stage, with inner layers using resins with lower char yields (5-15%) and outer layers using resins with higher char yields (25-35%), pre-establishing the porosity gradient before processing to simplify subsequent manufacturing steps
Solution Approach 2:
The invention systematically varies resin parameters (char yield, resin type) across different layers to create a controlled porosity gradient, transforming the complex problem of porosity control into a systematic parameter optimization approach that simplifies manufacturing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The porosity gradient fibrous preform enables efficient and uniform densification, reducing porosity and improving part density, especially in thick sections or complex geometries.
Implementation Method 1
the first resin is configured to be pyrolyzed to generate a first porosity in the first fabric-resin layer and the second resin is configured to be pyrolyzed to generate a second porosity in the second fabric-resin layer
Implementation Method 2
a first carbon powder and the first resin are configured to be pyrolyzed to generate the first porosity. In various embodiments, the porosity gradient fibrous preform further comprises a second carbon powder mixed with the second resin, and the second carbon powder and the second resin is configured to be pyrolyzed to generate the second porosity
Data Source
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Figure 5
AI summary
A porosity gradient fibrous preform (100) includes a first fabric-resin layer (102) having a first plurality of fibers (112) and a first resin (114a) and a second fabric-resin layer having a second plurality of fibers (112) and a second resin (114b), the second fabric-resin layer (104) being positioned further outward from a center of the porosity gradient fibrous preform (100) than the first fabric-resin layer (102). The first resin (114a) is different from the second resin (114b) so as to generate sequentially increasing porosity in the preform prior to a CVI densification step. The sequentially increasing porosity can be achieved, for example, by selecting resins for each layer with sequentially increasing moisture content, by selecting resins for each layer with sequentially decreasing char yield, and/or adding black carbon powder to interior located fabric-resin layers.